2001 f 150 ball joint?
 

How would I know if I have a bad ball joint?

i know on mine it would sqeak on bumps and turns.. one way to check is lift up front of the truck and stick a pry bar under the tire and lift up, If the tire lifts they are bad.

If there is more than 1/16" of play in it.

Or if your truck has over 100k on the originals odds are good they are ready.

Not to hijack but the bottom can be pressed out right? But the top cant?

Right.

Is it possible to press the ball joints out while the lower is still on the truck?

Lower Control Arm? Yea why would you take it off to press the joint out, that's a lot of unnecessary work

Yeah was getting a key made for mine and they did this showing my were bad. It's not cheap either:censored:

yep pretty easy to do. If/when you replace use MOOG. lifetime warr and they are about the best aftermarket you can get.
I think most parts stores carry the moog. they run about $45 each. if you do not mind ordering online goto www.rockauto.com they run about $25 each plus shipping.

directions to replace ball joint HERE

If you can see any movement between the ball and the socket of the ball joint, it is bad and should be replaced. You jack the truck at the front wheel "A" frame then put a breaker bar under the front tire and lift up. The ball should not move in the socket if the ball joint is good. (have a buddy lift while you watch the ball joint for movement). Be careful so as to not move the truck off the jack.